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Past attempts at energy efficiency?


mgbinspect
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I inspected a 1951 home yesterday with a basement packed to the gills with all kinds of old tools and equipment. The owner, who had passed, apparently really liked to tinker.

A couple things in particular came to the forefront as I tried to inspect this "tool time" museum:

About two weeks ago - I forget which thread - I had raised the question, "Why aren't (or weren't) there more after-market gadgets attempting to wring the heat out of the exhaust from furnaces and boilers? Well, lo and behold I ran across two of 'em both chocked on about 6' of oil-fired boiler exhaust - both abandoned, of course, so the brain trust was apparently right, they aren't useful.

Nonetheless, here they are:

The first one was a heavy gauge steel heat exchanger incorporated into the exhaust system with blower and ducts (the ducts have been removed).

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The second gadget was merely copper tubing coiled around the exhaust pipe with a metal jacket. I have no idea what he was doing with it, but it DID have a zone valve on it, so I don't think it had anything to do with a still...

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Those heat exchangers are fairly common around here, but I've never seen one that large. Here's my boilerplate: There is a heat recovery unit on the vent connector. These units cool the exhaust gasses, which can result in moisture condensing in the chimney, which can in turn cause deterioration of the chimney interior. The unit should be removed by a qualified HVAC technician.

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...These units cool the exhaust gasses, which can result in moisture condensing in the chimney, which can in turn cause deterioration of the chimney interior. The unit should be removed by a qualified HVAC technician.[/i]

Thank much!

Yeah, I gathered from the other thread that it wasn't a good idea, but this was the first one I had actually seen. Impressive construction, though. That's some serious steel! I suppose thermal mass was the aim?

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That's some serious steel! I suppose thermal mass was the aim?

I don't know. In addition to not having seen one that large, I've never seen one constructed of welded plate like that. Maybe it was insurance against the thing rusting out and dumping exhaust gasses into the basement.

This is more like what I typically see - much lighter construction. This particular one handled both the water heater and the boiler. The problem of the smaller vent being below the larger one aside, venting both into that confined and obstructed box couldn't be good.

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Here's a different type, without a heat exchanger. It's just a fan in an enclosure that surrounds the vent connector.

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I'm no HVAC guy by any means, but to look at one and imagine the big picture, the heat transfer rate has to be minuscule. How much heat can one of these things capture in one foot with the volume of air that 's moving through it via a fan? I suppose had they been able to run a computer model, they'd have abandoned the project while it was still in design phase.

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